268 PRINCIPLES OF SOIL MICROBIOLOGY 



the readily available nitrogen compounds of the soil, in the presence of 

 favorable sources of energy, thus exerting a very unfavorable action 

 upon the growth of higher plants. Rothe 118 stated that the fungi exceed 

 the bacteria and actinomyces, in acid as well as in neutral media, in 

 the assimilation of available nitrogen and in storing it away as micro- 

 bial organic matter; in the presence of CaC0 3 , large quantities of nitro- 

 gen added to the soil in the form of ammonium salts are transformed by 

 these organisms into very insoluble nitrogen compounds. The com- 

 petition between fungi and higher plants for the available nitrogen, 

 under certain conditions, was also pointed out by Hall and associates. 119 

 Hagem 120 found that Mucorales will readily assimilate ammonium 

 salts and transform them into microbial proteins. As pointed out above, 

 with cellulose or other carbohydrates as sources of energy, the fungi 

 may reassimilate 30 to 40 per cent of the carbon of the substrate 

 decomposed. This necessitates a parallel assimilation of nitrogen; 

 about one unit of available nitrogen is transformed into microbial 

 protein for every 30 units of cellulose decomposed. This leads to a 

 considerable reduction of the available nitrogen in the soil. 



Ehrenberg 121 stated that fungus protein is much less available for 

 further decomposition than bacterial protein, the fungus spores con- 

 taining a large quantity of nitrogen stored away in an unavailable 

 form, to some extent in the form of chitin, not readily subject to de- 

 composition. 122 Other investigations seem to point, however, that a 

 large part at least of the cell substance syntherized by fungi is as rapidly 

 decomposed as organic substances of animal origin. 1223 The disappear- 

 ance of the available nitrogen added to the soil in the form of ammon- 

 ium salts and nitrates is to be looked for more in the development of 

 fungi than of bacteria. Particularly is that true when these nitro- 



118 Rothe. Untersuchungen liber das Verhalten einiger Mikroorganismen 

 des Bodens zu Ammonium Salze und Natriumnitrat. Inaug. Diss. Konigsberg. 

 1904. 



119 Hall, A. D., Miller, N. H., and Gimmingham, C. T. Nitrification in acid 

 soil. Proc. Roy. Soc. (London), B, 80: 196-211. 1908. 



120 Hagem, 1908 (p. 237). 



121 Ehrenberg, P. Die Bewegung des Ammoniakstickstoffs in der Natur. 

 Mitt. Landw. Inst. Breslau, 4: 47-300. 1907. 



122 Wettstein, F. Das Vorkommen von Chitin und seine Verwertung als sys- 

 tematisch-phylogenetisches Merkmal im Pflanzenreiche. Sitz. Ber. Akad. 

 Wiss. Wien, Math. Nat. Kl. (I), 130: 3-20. 1921 (Centrbl. Bakt. II, 58: 329. 

 1923). 



122B Starkey, 1924 (p. 684). 



